Watch the Minor Blues 14 online guitar lesson by Brad Carlton from Bluesology 2
If you want to brighten up the dark sound of the minor blues, try playing a IV Dominant chord in bars 5 and 6. Listen to the sound of the sus chords, ninth chords, and other possibilities for this chord in progression 9. Also, take note of the flat II7 on the 3rd and 4th beats of bar 12.
A very slick turnaround in progression 10 is played in bars 11 and 12 with the flat II major 7th articulating both tension and at the same time a very cool resolution from the preceding flat VI 7th chord (V7 to I in B flat).